U.S. patent application number 13/171664 was filed with the patent office on 2011-10-20 for radio receiving apparatus.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Kazuhisa Obuchi, Akihide Otonari, Yoshinori Soejima.
Application Number | 20110255477 13/171664 |
Document ID | / |
Family ID | 38791983 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110255477 |
Kind Code |
A1 |
Otonari; Akihide ; et
al. |
October 20, 2011 |
RADIO RECEIVING APPARATUS
Abstract
A radio receiving apparatus for receiving the variable-length
RLC PDU data in an RLC layer includes the buffer memory sectioned
into a plurality of areas having a predetermined maximum data
length of the RLC PDU data. By referring to a sequence number SN
included in each received RLC PDU data, the radio receiving
apparatus stores the RLC PDU data having an identical sequence
number SN into an identical area, and assembles an RLC SDU data on
a basis of the RLC PDU data stored in each area.
Inventors: |
Otonari; Akihide; (Fukuoka,
JP) ; Soejima; Yoshinori; (Fukuoka, JP) ;
Obuchi; Kazuhisa; (Kawasaki, JP) |
Assignee: |
Fujitsu Limited
Kawasaki-shi
JP
|
Family ID: |
38791983 |
Appl. No.: |
13/171664 |
Filed: |
June 29, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11889833 |
Aug 16, 2007 |
8000348 |
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13171664 |
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Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04L 49/9094 20130101;
H04W 80/02 20130101; H04L 49/90 20130101; H04B 7/2603 20130101;
H04L 49/901 20130101; H04L 47/14 20130101; H04L 1/1812 20130101;
H04W 28/02 20130101; H04L 47/34 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04W 4/00 20090101
H04W004/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2006 |
JP |
2006-224107 |
Claims
1. A method for retransmitting data from a transmission apparatus
to a reception apparatus, comprising: the transmission apparatus
adding a sequential number, first information and second
information to each of the plurality of divided data which is
generated by dividing the data to be retransmitted; and the
transmission apparatus transmitting the plurality of divided data
including the sequential number, the first information and the
second information to the reception apparatus, wherein the first
information indicates the position of each of the plurality of
divided data in the data to be retransmitted, and the second
information indicates whether each of the plurality of the divided
data is last data in the plurality of the divided data.
2. A communication apparatus for retransmitting data to a reception
apparatus, comprising: a processor configured to add a sequential
number, first information and second information to each of the
plurality of divided data which is generated by dividing the data
to be retransmitted; a transmitter configured to transmit the
plurality of divided data including the sequential number, the
first information and the second information to the reception
apparatus, wherein the first information indicates the position of
each of the plurality of divided data in the data to be
retransmitted, and the second information indicates whether each of
the plurality of the divided data is last data in the plurality of
the divided data.
3. A method for transmitting data from a transmission apparatus to
a reception apparatus, comprising: the transmission apparatus
adding a sequential number, first information and second
information to each of the plurality of divided data which is
generated by dividing the data to be transmitted; and the
transmission apparatus transmitting the plurality of divided data
including the sequential number, the first information and the
second information to the reception apparatus, wherein the first
information indicates the position of each of the plurality of
divided data in the data to be transmitted, and the second
information indicates a retransmission request.
4. A communication apparatus for transmitting data to a reception
apparatus, comprising: a processor configured to add a sequential
number, first information and second information to each of the
plurality of divided data which is generated by dividing the data
to be transmitted; a transmitter configured to transmit the
plurality of divided data including the sequential number, the
first information and the second information to the reception
apparatus, wherein the first information indicates the position of
each of the plurality of divided data in the data to be
transmitted, and the second information indicates a retransmission
request.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2006-224107, filed on Aug. 21, 2006, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to radio receiving apparatus
for receiving a variable-length RLC PDU data in an RLC layer
belonging to Layer 2 forming a radio communication protocol layer,
and more particularly radio receiving apparatus enabling
efficiently storage of a received RLC PDU data into a buffer
memory.
[0004] 2. Description of the Related Art
[0005] A W-CDMA system becomes widely used today, as a third
generation (3G) radio communication system. Further, a standard
called HSDPA (High-Speed Downlink Packet Access) comes into
practical use to obtain high-speed (14 Mbps maximum) data
communication in W-CDMA. HSDPA is also called as 3.5G system
because of an improved version of the 3G system. The
standardization is carried out by 3GPP (the 3rd Generation
Partnership Project), an association for standardizing the 3G
system.
[0006] HSDPA has s the features of (1) shared use of one physical
channel by a plurality of mobile terminals (UE) in time division,
(2) automatic selection of higher speed modulation system and
coding system depending on an electric wave condition, (3) adopting
hybrid ARQ incorporating retransmission control (ARQ) combined with
correction coding processing, and so on.
[0007] FIG. 1 shows a diagram illustrating a data structure of
Layer 2 in the protocol architecture corresponding to HSDPA. Layer
2 is divided into sublayers of MAC (Medium Access Control)-hs,
MAC-d, and RLC (Radio Link Control).
[0008] FIG. 2 shows a diagram illustrating the format of RLC PDU
(Protocol Data Unit). RLC PDU shown in FIG. 2 is an Acknowledge
Mode RLC PDU enabling data delivery confirmation control and data
retransmission control. RLC PDU includes D/C bit for distinguishing
between a user data and a control data; a sequence number (SN)
indicating the sequential order of RLC-PDU; polling bit P
indicating the presence/non-presence of a delivery confirmation
request; area HE indicating information of the user data extension
area; length indicator LI; E bit; data storage area Data; and
padding bit PAD or piggyback (Piggybacked STATUS PDU).
[0009] The data size of RLC PDU is fixed to, for example, 42
octets, 82 octets or 122 octets (where 1 octet is 8 bits), which is
not changed during communication. RLC PDU is identified by the
sequence number SN, which has a numeric value ranging from, for
example, 0 to 4,095 maximum.
[0010] In RLC shown in FIG. 1, on the transmission side of RLC, a
transmission data RLC SDU (Service Data Unit) fed from an upper
layer is divided into a plurality of RLC PDUs, and forwarded to the
lower MAC-d layer, after a sequence number SN is given to identify
each RLC PDU.
[0011] Also, on the reception side of RLC, when the RLC PDUs are
received from the lower MAC-d layer, by being sorted in order of
the sequence number SN, the RLC PDUs are merged to assemble RLC
SDU, and then transferred to the upper layer. At this time, when
there is a missing sequence number SN, a retransmission request of
RLC PDU corresponding to the missing SN is initiated.
[0012] Therefore, the transmission side of RLC is required to
retain the transmitted RLC PDU in a buffer (memory) until the
notification of delivery confirmation is received from the
reception side of RLC. Also, the reception side of RLC is required
to keep a buffer for the RLC PDU of which SN is missing, when
performing RLC SDU assembly.
[0013] FIG. 3 shows a diagram illustrating the operation on the
reception side of RLC in the HSDPA system specified by 3GPP. In the
present and subsequent figures, "H" denotes an RLC Header, and
"Data" denotes a Payload.
[0014] When a missing sequence number is detected on the reception
side of RLC, the transmission side is notified of the missing
sequence number SN of the RLC PDU concerned, in the form of a
retransmission request. As shown in FIG. 3(a), for example, SN=2 is
missing, and the retransmission request therefor is initiated. At
this time, on the reception side of RLC, a buffer area for
originally storing RLC PDU of SN=2 is kept idle. The buffer size to
be kept idle can easily be obtained because of the fixed length of
RLC PDU. When the reception side of RLC receives RLC PDU of SN=2 as
a retransmission data [refer to FIG. 3(b)], the received PDU is
allocated in the buffer area having been kept idle for the PDU
concerned, and the assembly of RLC SDU is performed [refer to FIG.
3(c)].
[0015] In Japanese laid-open Patent Publication No. 2006-20044,
there is disclosed a memory management method in the MAC-hs
sublayer, enabling reduction of the increase of the memory amount
without need of a complicated memory control method, by dividing a
variable-length MAC-hs PDU into each unit of RLC PDU and storing
into a shared memory (buffer) together with a sequence number.
[0016] After the realization of the above-mentioned 3.5G mobile
communication systems by HSDPA, subsequently, migration to the
fourth generation (4G) systems will be expected in early stages so
as to realize higher speed and larger capacity. However, in the
present estimation, one more stage called as "3.9G" (which may also
be called as "Super 3G") will be introduced before migration to 4G
systems. As the communication speed of the 3.9G systems, a maximum
speed of 100 Mbps, or of that order, is assumed. In 3GPP at
present, as the 3.9G specification, a study is in progress to
modify RLC PDU from fixed length, as shown in FIGS. 1, 2, to
variable length.
[0017] FIG. 4 shows a diagram illustrating an assumed configuration
of the RLC sublayer when the RLC PDU is modified to have variable
length. As shown in FIG. 4, when the RLC PDU is modified to have
variable length, the sequence number SN is used as a number to
identify RLC SDU. To identify RLC PDU constituting each RLC SDU,
assumedly, an SI (Segment Indicator) is introduced. In case of the
fixed-length RLC PDU, the number of RLC PDUs constituting a
fixed-length RLC SDU is uniquely determined. Accordingly, the RLC
SDU can be identified when the RLC PDU is identified. However, when
the RLC PDU is modified to have variable length, the number of RLC
PDUs constituting each RLC SDU is not uniquely determined.
Therefore, it becomes necessary to introduce any symbol so as to
identify RLC SDU further. Thus, the sequence number SN
conventionally used to identify each RLC PDU is used as a symbol to
identify RLC SDU, and the aforementioned segment indicator SI is
newly introduced as the symbol to identify RLC PDU.
[0018] FIG. 5 shows an exemplary format when RLC PDU is modified to
have variable length. As described above, when RLC PDU is modified
to have variable length, the sequence number SN becomes the number
to identify RLC SDU, and RLC PDU is to be identified by the
combination of the above sequence number SN and the segment
indicator SI belonging thereto.
[0019] In the format, the reason for providing a plurality of areas
for the segment indicator SI is that, when the RLC PDU being
divided into a variable length is further divided, additional
attachment of the segment indicator SI becomes necessary to
identify further divided RLC PDU. At the retransmission control
when RLC PDU is modified to have variable length, the following
problem will be produced.
[0020] FIG. 6 shows a diagram explaining the operation on the
reception side of RLC when the RLC PDU is modified to have variable
length. When a missing RLC PDU is detected on the reception side of
RLC, the transmission side is notified of both the sequence number
SN and the segment indicator SI corresponding to the above missing
RLC PDU, as a retransmission request. As shown in FIG. 6(a), for
example, in case of a missing RLC PDU of SN=0, SI=1, the
retransmission thereof is requested. At this time, because the data
length of the missing RLC PDU is unknown, it is not possible to
keep an idle buffer area for the missing RLC PDU so as to store RLC
PDUs in order of the segment indicator SI [refer to FIG. 6(b)].
[0021] Assuming to keep the idle buffer area beforehand, it is
necessary to assume to receive RLC PDU having a preset maximum
length, which results in a high possibility of wasteful buffer area
consumption.
[0022] In Patent document 1, a variable-length MAC-hs PDU is
divided into each fixed-length RLC PDU, which does not produce any
problem because the RLC PDU is divided later in the RLC sublayer.
However, it is not possible to apply the same method in an upper
layer than the RLC sublayer because of no data division performed.
Also, in the high-speed communication such as Super 3G, efficient
communication can be achieved by elongating each data length, and
therefore, it is not preferable to introduce excessive division of
data.
[0023] FIG. 7 shows a diagram explaining a use state of the buffer
area considering the maximum length of the RLC PDU. For example,
assuming the maximum length of the RLC PDU is 1,500 bytes, it is
necessary to prepare a buffer area of 1,500 bytes for one RLC PDU.
Thus, the buffer areas shown by the broken lines in the figure are
wasted.
[0024] Also, when storing RLC PDUs in a packed manner in order of
reception, RLC PDUs having an identical sequence number SN may not
always be received consecutively. When RLC PDUs of different
sequence numbers SN are received mixed, it is necessary to assemble
RLC SDU after extracting RLC PDUs having an identical sequence
number SN. Thus, the assembly to RLC SDU becomes complicated.
[0025] Accordingly, it is an object of the present invention to
provide radio receiving apparatus in case of the variable-length
RLC PDU, enabling efficient storage of received RLC PDUs into the
buffer without wasting the buffer area.
SUMMARY OF THE INVENTION
[0026] As a first configuration of the radio receiving apparatus
according to the present invention to achieve the aforementioned
object, in the radio receiving apparatus which receives a
variable-length RLC PDU data in an RLC layer belonging to Layer 2
forming a radio communication protocol layer, and assembles one RLC
SDU data from one or a plurality of RLC PDU data, there are
provided a buffer memory having a predetermined maximum data length
of the RLC SDU data and being sectioned into a plurality of areas;
and a controller referring to first sequence information included
in the header of the received RLC PDU data, storing the RLC PDU
data having the identical first sequence information into an
identical buffer memory area, and assembling the RLC SDU data on a
basis of the RLC PDU data stored in each area.
[0027] As a second configuration of the radio receiving apparatus
according to the present invention, in the above first
configuration, when storing the plurality of RLC PDU data into one
buffer memory area, the controller stores the plurality of RLC PDU
data into the above area in order of reception, and to assemble the
RLC SDU data, the controller successively reads out the plurality
of RLC PDU data in order of the sequence identified by second
sequence information being included in each header of the plurality
of RLC PDU data stored in the above area, sorts in order of the
above sequence, and assembles the RLC SDU data.
[0028] As a third configuration of the radio receiving apparatus
according to the present invention, in the above second
configuration, there are provided a management memory storing the
second sequence information, the top address and the data length of
each RLC PDU data stored in each buffer memory area as a set of
data, and the controller successively records the set of data
including the second sequence information, the top address and the
data length of each RLC PDU data, in order of reception of the
plurality of RLC PDU data.
[0029] As a fourth configuration of the radio receiving apparatus
according to the present invention, in the above third
configuration, when the reception sequence of the plurality of RLC
PDU data is continuous in the regular order of the second sequence
information, with regard to the plurality of RLC PDU data having
the consecutive second sequence information, the controller records
into the management memory the second sequence information of the
first RLC PDU data, the second sequence information of the last RLC
PDU data, the top address of the first RLC PDU data, and the data
length of the entire plurality of RLC PDU data having the
consecutive second sequence information, as a set of data.
[0030] As a fifth configuration of the radio receiving apparatus
according to the present invention, in the above second
configuration, when storing the plurality of RLC PDU data into one
buffer memory area, the controller stores into the buffer memory of
which address is identified by the first sequence information and
top address information included in each header of the above
plurality of RLC PDU data, and reads out the plurality of RLC PDU
data in order of storage of the plurality of RLC PDU data stored in
the above area, and assembles the RLC SDU data, and further, the
top address information is given according to the transmission
sequence and the data length of the plurality of RLC PDU data.
[0031] As a sixth configuration of the radio receiving apparatus
according to the present invention, in the above fifth
configuration, on receiving through retransmission control an RLC
PDU data having top address information identical to the buffer
memory address in which the RLC PDU data is already stored, the
controller overwrites the received RLC PDU data on the buffer
memory address identified by the above top address information.
[0032] As a seventh configuration of the radio receiving apparatus
according to the present invention, in the above first
configuration, the first sequence information is a sequence number
identifying an RLC SDU data.
[0033] According to the present invention, when the RLC PDU data in
the RLC layer is modified to have variable length, a buffer memory
for storing the RLC PDU data received in radio receiving apparatus
can be used efficiently without being wasted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 shows a diagram illustrating a data structure of
Layer 2 in the protocol architecture corresponding to HSDPA.
[0035] FIG. 2 shows a diagram illustrating an RLC PDU format.
[0036] FIG. 3 shows a diagram illustrating the operation on the
reception side of RLC in the HSDPA system specified by 3GPP.
[0037] FIG. 4 shows a diagram illustrating an assumed configuration
of the RLC sublayer when the RLC PDU is modified to have variable
length.
[0038] FIG. 5 shows an exemplary format when the RLC PDU is
modified to have variable length.
[0039] FIG. 6 shows a diagram explaining the operation on the
reception side of RLC when the RLC PDU is modified to have variable
length.
[0040] FIG. 7 shows a diagram explaining a use state of a buffer
area considering the maximum length of the RLC PDU.
[0041] FIG. 8 shows a configuration diagram of radio receiving
apparatus according to an embodiment of the present invention.
[0042] FIG. 9 shows a diagram illustrating an exemplary
configuration of an RLC buffer according to an embodiment of the
present invention.
[0043] FIG. 10 shows a diagram illustrating another management form
using a management memory for managing the RLC PDUs being stored in
an RLC buffer 11 on a basis of the sequence number SN.
[0044] FIG. 11 shows a diagram illustrating another exemplary RLC
PDU format and an exemplary RLC buffer configuration according to
an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] The preferred embodiments of the present invention are
described hereinafter referring to the charts and drawings.
However, the embodiments described below are not intended to limit
the technical scope of the present invention. FIG. 8 shows a
configuration diagram of radio receiving apparatus according to an
embodiment of the present invention. The radio receiving apparatus
is a radio communication terminal unit 10 or a radio base station
unit 20. Radio communication terminal unit 10 and radio base
station unit 20 respectively includes RLC buffers 11, 21, and RLC
controllers 12, 22 for performing readout control and write control
thereto. The embodiment described in the following is a buffer
configuration and buffer control on the reception side of RLC. In
case of application to a downlink such as HSDPA, radio
communication terminal unit 10 is the radio receiving apparatus of
the present invention. Meanwhile, in case of application to an
uplink such as HSUPA, radio base station unit 20 is the radio
receiving apparatus of the present invention. Hereafter, the
description is made using RLC buffer 11 and RLC controller 12 of
radio communication terminal unit 10 as an example. However, the
embodiment of the present invention is also applicable to RLC
buffer 21 and RLC controller 22 of radio base station unit 20. RLC
controllers 12, 22 may be configured of either hardware or
software, or the combination thereof.
[0046] FIG. 9 shows a diagram illustrating an exemplary
configuration of the RLC buffer according to the embodiment of the
present invention. RLC buffer 11 is sectioned on a basis of the
sequence number SN identifying an RLC SDU. For each SN, a buffer
amount having a predetermined maximum RLC SDU length (for example,
1,500 bytes) is given.
[0047] RLC PDUs are transmitted in the format shown in the above
FIG. 5, having a header including a sequence number SN and a
segment indicator SI. When receiving the RLC PDUs,
[0048] RLC controller 12 refers to the sequence number SN included
in the header of each RLC PDU, distributes the RLC PDUs on a basis
of SN, and stores the received RLC PDUs into each buffer area
assigned to each SN.
[0049] Because the maximum length of each RLC PDU is predetermined,
by distributing the RLC PDUs on a basis of each sequence number
identifying each RLC SDU, the RLC PDUs can be efficiently stored
into RLC buffer 11 without considering the data lengths of the
variable-length RLC PDUs. Typically, by distributing the RLC PDUs
on a basis of each SN, a plurality of RLC PDUs can be stored on a
basis of each sequence number. As long as the sequence number SN is
identical, the data length of the entire RLC PDUs having the
identical sequence number SN can be stored without exceeding the
maximum RLC SDU length. Thus, it is possible to store the
variable-length RLC PDUs into RLC buffer 11 as efficiently as
possible.
[0050] In FIG. 9(a), it is assumed that the RLC PDUs are received
in order of (1) SN=0, SI=0, (2) SN=1, SI=0, (3) SN=0, SI=2, and (4)
SN=0, SI=1, similar to FIG. 6. Then, the RLC PDUs of (1) SN=0,
SI=0, (3) SN=0, SI=2, and (4) SN=0, SI=1 are stored into an area
assigned to SN=0 in RLC buffer 11 in order of reception, while the
RLC PDU of (2) SN=1, SI=0 is stored into an area assigned to SN=1
in RLC buffer 11. The RLC PDUs of (3) SN=0, SI=2, and (4) SN=0,
SI=1 are stored in order of reception, though the reception
sequence is reversed due to retransmission.
[0051] FIG. 9(b) is information stored in the management memory for
managing RLC buffer 11. The management memory is, for example, an
internal memory of RLC controller 12. Or, a portion of the area of
RLC buffer 11 may be used as management memory. Or otherwise, it
may also be possible to provide a dedicated memory for the
management memory.
[0052] In the management memory also, the RLC PDUs stored in RLC
buffer 11 are managed on a basis of each sequence number SN. In the
management memory, there are stored a top address, a data length,
and bit information (LSI: Last Segment Indicator) indicative of the
last segment indicator SI in the sequence number SN concerned, for
each segment indicator SI of RLC PDU.
[0053] For each sequence number SN, when the entire RLC PDUs up to
the RLC PDU of LSI=1, having the last segment indicator SI, are
completely stored in RLC buffer 11, RLC controller 12 refers to the
management memory shown in FIG. 9(b), and reads out from the top
address of each RLC PDU in order of the segment indicator SI. Thus,
RLC controller 12 sorts RLC PDUs in order of the segment indicator
SI, and assembles an RLC SDU.
[0054] In FIG. 9(a), with regard to the RLC PDUs having a sequence
number SN=0, RLC controller 12 reads out in order of the segment
indicator SI, namely, in order of (1) SN=0, SI=0, (4) SN=0, SI=1
and (3) SN=0, SI=2, so as to assemble the RLC SDU.
[0055] FIG. 10 shows a diagram illustrating another management form
using a management memory for managing the RLC PDUs being stored in
an RLC buffer 11 on a basis of each sequence number SN. The
management memory shown in FIG. 10 includes an area capable of
storing a range having consecutive segment indicators SI. An area
"a" stores the first SI and the last SI of the consecutive segment
indicators SI. As shown in FIG. 10(a), as to an RLC PDU having a
sequence number SN=0, when the RLC PDU having SI=0 is received, an
identical SI=0 is stored in the area "a" as the consecutive first
SI and the last SI because only one RLC PDU has been received so
far. Also, the top address of the RLC PDU having SI=0 is stored,
together with the data length thereof.
[0056] Subsequently, when an RLC PDU having SI=1 consecutive from
SI=0 is received, in the area "a", there are stored SI=0 as the
first consecutive SI, and SI=1 as the last SI. The top address
remains the top address of the RLC PDU having SI=0, and as the data
length, a total data length of the RLC PDU having SI=0 and the RLC
PDU having SI=1 is stored.
[0057] When RLC PDUs are received in order of the segment indicator
SI, and stored in RLC buffer 11 in order of the segment indicator
SI, the consecutive plurality of RLC PDU can be read out by
specifying the top address and the data length. Thus, it is
possible to manage the RLC PDUs stored in RLC buffer 11 with a
smaller amount of data, as compared to storing the top address and
the data length for each segment indicator SI, by which the memory
capacity of the management memory can be reduced. In case of FIG.
10(b), by storing the top address of SI=0 and the total data length
of SI=0 and SI=1, it is possible to manage two RLC PDU of SI=0 and
SI=1 which are stored consecutively using one set of data.
[0058] In FIG. 10(c), further, an RLC PDU having SI=2 consecutive
from SI=1 is received, and in the area "a", there are stored SI=0
as the consecutive first SI, and SI=2 as the last SI. As the top
address remains the top address of the RLC PDU having SI=0, and as
data length, the total data length of RLC PDU from SI=0 to SI=2. As
such, as long as the segment indicators SI are consecutive, it is
possible to manage the plurality of RLC PDUs consecutively stored,
using one set of data, and thus, the memory capacity of the
management memory can be reduced.
[0059] FIG. 11 shows a diagram illustrating another exemplary RLC
PDU format and an exemplary RLC buffer configuration according to
an embodiment of the present invention. In the exemplary RLC PDU
format shown in FIG. 11(a), a segment pointer SP is employed in
place of the segment indicator SI shown in FIG. 5. The segment
pointer SP is an offset address from the top address of each buffer
area of RLC buffer 11 for each sequence number SN.
[0060] RLC buffer 11 is sectioned in advance on a basis of the
maximum length of the RLC PDU (for example, 1,500 bytes), and the
address range of the buffer area corresponding to each sequence
number can be identified. Accordingly, by specifying the storage
positions of the plurality of RLC PDUs for each sequence number SN
by use of the address, each RLC PDU can be stored in order, even if
the RLC PDU has variable length.
[0061] As shown in FIG. 11(b), for example, with regard to the
sequence number SN=0, when RLC PDUs specified by the segment
pointers (1) SP=0.times.0000, (2) SP=0.times.0100 and (3)
SP=0.times.01A0 are received, the storage is performed into the
buffer area of SN=0, using each address specified by each segment
pointer SP as top address. Even when the reception sequence is not
the original sequence of (1), (2), (3), but the reception is made,
for example, in order of (1), (3), (2), RLC controller 12 stores
the RLC PDU of (1) SP=0.times.0000 into the address specified by
the segment pointer SP, and also stores the next received RLC PDU
of (3) SP=0.times.01A0 into the address specified by the segment
pointer SP. At this time, in the buffer area, there is an idle
buffer area for the RLC PDU of (2) SP=0.times.0100 between the RLC
PDU of (1) SP=0.times.0000 and the RLC PDU of (3) SP=0.times.01A0.
On receipt of the RLC PDU of (2) SP=0.times.0100, the storage is
made in the address specified by the segment pointer SP (2)
SP=0.times.0100, and thus, the RLC PDUs are stored in the buffer
area in order of (1) SP=0.times.0000, (2) SP=0.times.0100 and (3)
SP=0.times.01A0.
[0062] In the format shown in FIG. 11(a), an LSI bit defined next
to the segment pointer SP is a bit for identifying the last RLC PDU
among RLC PDUs of each sequence number SN. RLC controller 12
recognizes that the RLC PDU having LSI=1 is the last RLC PDU of the
sequence number SN concerned, and confirms whether or not the
entire RLC PDUs corresponding to the sequence number SN have
already been received and stored in the areas preceding the storage
position of the RLC PDU having LSI=1, of the buffer area of the
sequence number SN concerned. When the entire RLC PDUs are already
stored, RLC controller 12 reads out in the regular order of the
storage, and assembles RLC SDU. When the entire RLC PDUs are not
stored yet, RLC controller 12 performs processing to store the
entire RLC PDUs by standing by further, or initiating a
retransmission request, or the like.
[0063] As such, by identifying each RLC PDU and storing into the
buffer area using the segment pointer SP, that is, the top address
in which each RLC PDU is stored in the buffer area, it is possible
to store the RLC PDUs into RLC buffer 11 in order of transmission.
Namely, even when the reception sequence is replaced, it is
possible to store in order of transmission.
[0064] Also, when a portion of the RLC PDUs is/are not received,
RLC controller 12 initiates a retransmission request of the above
RLC PDU(s) to the transmission side. When the RLC PDU of interest
is received with delay after the initiation of the retransmission
request, an identical RLC PDU is received twice, based on the above
retransmission request. In the above case, the identity decision is
made, for example, by comparing information identifying each RLC
PDU such as the segment indicator SI. In case of being identical,
it becomes necessary to discard one. However, such the above
discard processing becomes unnecessary when using the segment
pointer SP.
[0065] Namely, even when an identical RLC PDU is received twice, by
overwriting in the address specified by the segment pointer SP,
only one of the identical RLC PDUs can be stored automatically.
Thus, the identity decision processing of the two RLC PDUs and the
discard processing become unnecessary.
[0066] Also, when the retransmission request is made, there is a
case of transmission by being divided further at the time of the
retransmission. In such a case, it becomes necessary to form the
segment indicator SI with a hierarchical structure (for example,
assuming the segment indicator of RLC PDU being retransmission
requested to be SI=1, the segment indicators of the two RLC PDUs
further divided and retransmitted are set to be SI=1-1 and SI=1-2,
or the like), and to add the segment indicator SI area in the
header.
[0067] In contrast, when using the segment pointer SP, even when
the RLC PDU to be retransmitted is further divided, the top address
of the buffer area to store each divided RLC PDU may be specified
as segment pointer SP. Thus, no additional header area is needed,
and instead, only to store each RLC PDU into the address specified
by the segment pointer SP is needed. Moreover, even when the
divided data length of each RLC PDU is unknown because of the
redivision, it is not necessary to modify the configuration of RLC
buffer 11.
[0068] The foregoing description of the embodiments is not intended
to limit the invention to the one details of the examples
illustrated. Any suitable modification and equivalents maybe
resorted to the scope of the invention. All features and advantages
of the invention which fall within the scope of the invention are
covered by the appended claims.
* * * * *